EP0634516B1 - Method for and apparatus producing coatings from plastic in particular for floor coverings - Google Patents

Description

For the production of coverings in the form of sheets, plates, for soil in particular, it has been proposed for a long time to use plastics.

Among the different techniques used to carry out such coatings, and more particularly floor coverings, it has been proposed to coat a continuous support (complex consisting of a grid glass yarn + a nonwoven), then, to deposit, continuously on the surface said support thus coated, granules, PVC for example, the whole being calendered and passing through an actual processing tunnel (infrared heating + calendering), followed by cooling for then be grained and receive a final surface treatment. This process, which has the advantage of allowing continuous production, high speed, and leads to floor coverings having very good characteristics (resistance to wear, to puncture), present however, a limit in that it leads to products of uniform appearance which, at best, can present as decor a "granita" effect if particles with different colors are used. However, with such a technique, it is not possible to obtain decorations, contours determined, although this has been envisioned for almost a century as that emerges from DE-C-138390, having different colors, except to realize a real surface impression on the floor covering previously realized as shown in particular from FR-A-2 336 187.

Various proposals have been made in the past to achieve directly colored patterns during the continuous production of plastic-based sheets. Thus, the patents US-A-4,076,567 and FR-A-2 542 260, allow to make plastic sheets decorated by spraying a powder onto a support through a frame screen printing either flat (US-A-4,076,567) or rotary (FR-A-2,542,260). The powder deposition being carried out without contact between the support and the frame screen printing, it is thus possible to obtain colored patterns. These techniques therefore make it possible to obtain structures having patterns formed in the mass of the sheet produced, but show however, a number of drawbacks.

The solution described in US Pat. No. 4,076,567 allows the use of plastic particles (PVC for example) which can be coarse (dimensions can be from two micrometers to about four millimeters) (see column 6 lines 50 to 55), but the distribution system using a flat, fixed frame, similar to that used for printing fabrics, is that this frame is not in contact with the support, has as disadvantage of implying an advance intermittently and above all can lead to a distortion of the patterns produced during the advance of the support if the frame is not raised, which then further complicates the implementation of the process.

The solution described in French patent FR-A-2,542,260 is attractive by the fact that the use of a rotary screen printing frame allows a deposits at high speed and increases production capacity, due to then it is possible to work without downtime with a continuous movement, at constant speed, of the support to be decorated.

Generally, according to this technique, the removal is carried out without contact between the support and the screen printing frame (as in the aforementioned US patent), the frame being supplied by through a hopper located inside the latter, hopper which has two doctor blades in contact with the cylinder. We can say that she also matches the frame printing technique rotary used for the decoration of textile fabrics. Compared to the decoration of textile fabrics, the adaptations made consist in using not dyes, but to deposit on the support, by gravity, powders contained inside a hopper, which are conveyed to the interior thereof by a rotating screw device.

The quantity of powder deposited is adjustable according to the size meshes of the screen printing frame and the opening of the lips of the inner hopper (distance between the two lips).

• résines (PVC émulsion, PVC suspension),
• plastifiants,
• stabilisants,
• pigments,
• oxydes de titane,
• noir de fumée.. .

Such a technology is however limited to applications of powder of small particle size, typically dry mixing of PVC of composition:

• resins (PVC emulsion, PVC suspension),
• plasticizers,
• stabilizers,
• pigments,
• titanium oxides,
• smoke black ...

Furthermore, in all the examples given in this document, we do not can only obtain low weight items of the order of 500 g / m2 + 30 g / m2.

Given the value of such a technology removal through a rotating frame, it could have been considered to adapt it to produce "encrusted" products made up of at least two components of different colored granules, allowing to obtain complex, usable as floor coverings, and which have a thickness of at least one millimeter, must be produced in large width (more than two meters) and have a high weight (of from 1250 g / m2 to 2500 g / m2.

Tests carried out on an installation reproducing the lessons of French patent FR-A-2,542,260 for producing such products, however demonstrated that such a procedure was not transposable industrially when it was desired to deposit particles of plastic material which may have large relative dimensions, greater than one millimeter, as in US-A-4,076,567.

• d'une mauvaise régularité longitudinale de la dépose des granulés résultant du "faux-rond" que présente un tel cadre rotatif ;
• d'une mauvaise régularité transversale de la dépose de ces granulés, par suite de la déformation de la génératrice dudit cadre rotatif ;
• d'une pollution des motifs obtenus par des granulés d'une autre couleur, compte tenu qu'il se produit un déplacement relatif entre le cadre et le support sur lequel sont disposés les granulés ;
• d'une surépaisseur parasite à l'arrière de chaque motif due à la chute des granulés situés sur une zone non perforée et ;
• d'une limitation dans la dimension et les formes des motifs réalisables par suite d'un écoulement parasite transitoire.

Indeed, it has been observed that by implementing such technology, it was not possible to produce a synthetic coating, of floor or wall, of good quality as a result:

• poor longitudinal regularity of the deposition of the granules resulting from the "runout" that such a rotary frame has;
• poor transverse regularity of the deposition of these granules, as a result of the deformation of the generator of said rotary frame;
• pollution of the patterns obtained by granules of another color, given that there is a relative displacement between the frame and the support on which the granules are arranged;
• a parasitic excess thickness at the back of each pattern due to the fall of the granules situated on an unperforated area and;
• a limitation in the size and shapes of the patterns achievable as a result of transient stray flow.

In addition, such technology does not allow the removal of products abrasives, frequently used in floor coverings, to obtain non-slip products or usual effects. Indeed, by the fact that the regulation system consists of a hopper whose lips are in contact with the frame, the use of abrasive products would cause significant wear and, therefore, very rapid deterioration of all.

Now we have found, and this is what is the subject of the present invention, a solution that solves these problems, and allows, share, the realization of products at very high speed of production of similar to the rotary frame technique and on the other hand the use of large particles, as in the flat frame removal technique (US-A-4,076,567).

The process and installation for the production of complexes usable as conformal floor coverings to the invention include the features as defined in the independent claims 1 and 4 respectively, with any preferred embodiment as defined in the dependent claims.

According to an embodiment according to the invention, the strip deformable has a structure similar to the screen printing sheets used for a rotary frame, this strip being positioned on three rolls of two of which define a plane parallel to the surface to be coated, and the third, arranged in the median plane of the two aforementioned rollers, ensuring the tension of said strip by a vertical translation.

In a preferred embodiment, according to the invention, the lips of the chute are in contact with the screen or shaped screen strip, this contact being located at a level below the plane defined by the lower generators of the guide rollers and maintaining the bandaged.

• les figures 1 et 2 sont respectivement des vues en élévation et de côté d'un ensemble permettant la distribution selon un type déterminé de granulés de matière plastique sur un support conformément à l'invention, en vue de réaliser un revêtement de sol ;
• la figure 3 est une vue schématique, vue de côté, illustrant la manière dont est assurée la régularité de dépose des granulés sur une machine réalisée conformément à l'invention ;
• la figure 4 est une vue de détail, schématique, montrant la manière dont est réalisée la dépose des granulés sur le support.

The invention and the advantages which it provides will however be better understood thanks to the embodiment given below of an installation allowing its implementation, and which is illustrated by the appended figures in which:

• Figures 1 and 2 are respectively elevational and side views of an assembly for the distribution according to a determined type of plastic granules on a support according to the invention, for producing a floor covering;
• Figure 3 is a schematic view, side view, illustrating the manner in which is ensured the regularity of depositing the granules on a machine produced according to the invention;
• Figure 4 is a detail view, schematic, showing how the granules are deposited on the support.

An installation allowing the implementation of the conforming process to the invention, is in the form of an assembly comprising essentially means for depositing on a support coating (complex consisting of a glass wire grid plus a nonwoven for example), plastic granules which are then tablets and heat treated to make a sheet homogeneous which is then received in the form of a roll of great length.

In accordance with the invention, the means for depositing the granules are constituted by a succession of organs for distributing granules which, according to the invention, are produced as illustrated in Figures 1 and 2. Each distribution assembly comprises as essential element a deformable strip (3) of the same kind as a hollow cylinder used to make a rotating frame.

This strip is positioned on three rollers marked (1), (4) and (6). The tension of the deformable strip is ensured by vertical translation of the roller (1). The drive of the strip is ensured by the roller (6) which is equipped with a motorization. The biasing of the roller (1) makes it possible to adjust guiding the strip during its movement.

The printing machine is equipped with an inner hopper vibrating (2) comprising a chute having two rigid lips (12) in contact with the deformable strip (3). The vibration of the hopper is a unidirectional vibration horizontal displacement parallel to the generating lip / chute contact.

A feeding device (not shown on the document appendix), allows the hopper to be filled uniformly over its entire width and maintain a constant level inside of it.

The printing machine is equipped with a suction device (7) located between the hopper (2) and the motorized roller (6). This device allows recover the granules remaining inside and outside the strip deformable (3). Its role is therefore to clean the tape. The frame (7 ') allows the use of a large suction without disturbing the mattress of granules previously deposited.

The granules are deposited by gravity and vibration.

The support (13), on which the granules are deposited, is not in contact with the deformable strip (3). It is supported by the mat (5).

The scrolling speeds of the support, the belt (5) and the strip deformable (3) are identical.

All the advantages of such a procedure that one could qualify as a "moving web" impression, stem from the fact that its work surface is flat.

The seal between the hopper lips (12) and the deformable strip (3) is ensured by the tension of the latter. Indeed, the contact between the lips and the strip being situated at a level below the plane defined by the lower generators of the rollers (4) and (6), the tension of the strip creates a pressure force distributed uniformly over the contact generator lips / strip. It is the position of the hopper lips that ensures fixed positioning of the lip / strip contact generator (see figure 3).

Thanks to such a procedure, the advantages are obtained following:

Longitudinal regularity of removal.

Indeed, the tension of the strip (3), which has a certain elasticity and which does not have a rigid part, ensures a constant air gap and minimum between the lips (12) of the hopper and the strip (3).

In addition, the contact generator lip (12) / strip (3) is fixed because its position is determined by that of the hopper lips which are as to they are rigid.

This avoids the cyclic phenomenon induced by the runout present on a rotary screen printing frame.

The longitudinal regularity of the removal is therefore strongly improved.

Transverse regularity of the deposit, given that the pressure force of the rigid lips (11) of the hopper, exerted on the deformable strip (3), does not deform the generator of lip / strip contact. Indeed, the latter is not embedded at its ends therefore, under the pressure force of the lips, it moves vertically but remains perfectly straight.

In addition, the design of the hopper fixing device does not not require great precision as to the positioning of the lips of the hopper in relation to the belt. Indeed, the lip / strip contact can take place on a whole plane. This is not the case when using a rotating frame which requires positioning along a line (the lower generator of the engraved cylinder).

• l'effort de pression exercé entre les lèvres de la trémie et la bande déformable ;
• le positionnement des lèvres de la trémie par rapport à la bande.

The transverse regularity of the deposit is therefore greatly improved. In fact, the lip / strip air gap remains constant over the entire dusting width, whatever:

• the pressure force exerted between the lips of the hopper and the deformable strip;
• the positioning of the hopper lips relative to the strip.

No pollution in the design formed.

This absence of pollution can be explained as follows by referring to Figure 4 attached.

Between the moment when the granules (14) pollute the frame (under the hopper interior) and when they are collected by the suction device (7), the portion of the strip (3), on which they are fixed, remained horizontal and it moved parallel to the support (13) on which the granules are deposited.

• les granulés (14a) (situés à l'intérieur de la bande), qui passent entre les lèvres de la trémie et les surfaces non perforées (15) de la bande (3), ne peuvent pas retomber sur le support (3) : ils sont tous récupérés par le dispositif d'aspiration (7) ;
• les granulés (14b) situés à l'extérieur de la bande (3), présents uniquement dans les zones perforées (16) de celle-ci, ne peuvent pas, en retombant, polluer les dessins réalisés : entre la trémie (2) et le dispositif d'aspiration (7), les zones non perforées (15) de la bande (3) restent positionnées à la verticale des zones vierges et protègent ainsi ces dernières de toute pollution.

Therefore :

• the granules (14a) (located inside the strip), which pass between the lips of the hopper and the non-perforated surfaces (15) of the strip (3), cannot fall on the support (3): they are all recovered by the suction device (7);
• the granules (14b) located outside the strip (3), present only in the perforated areas (16) thereof, cannot, by falling, pollute the drawings made: between the hopper (2) and the suction device (7), the non-perforated areas (15) of the strip (3) remain positioned vertically above the blank areas and thus protect the latter from any pollution.

The use for producing the patterns of such a continuous strip moved and held parallel opposite the support to be coated, therefore completely eliminates the risk of polluting a motif with granules of different color. In addition, it removes the parasitic excess thicknesses located at the back of each design. These excess thicknesses are due, when using a rotating frame, to the fall granules passing between the lips of the hopper and the surfaces not perforated with the deformable strip.

The parallel movement of the strip and the support allows also to space the suction device considerably and the hopper. This therefore makes it possible to clean the deformable strip without disturbing the flow of granules.

Very good flow of granules , obtained through the use of a vibrating hopper (2) which promotes constant flow, minimizes the duration of the transient flow of granules. This vibration, which occurs according to the contact generator lips / strip, does not cause fatigue phenomenon of the deformable strip. In fact, this vibration does not induce any additional internal stress on the strip.

The use of a band therefore allows, thanks to the vibration of the hopper, to obtain patterns of small dimensions while filling a good regularity of thickness of the product obtained.

Thus, the realization of patterns of dimensions and shapes very can be considered. Indeed, in this configuration, the mass of granules deposited is completely independent of the dimensions of the zones non-perforated with the deformable strip.

• très bonne régularité longitudinale de la dépose (pas de faux-rond),
• très bonne régularité transversale de la dépose (pas de déformation de la génératrice de contact lèvres/bande et pas de parallélisme rigoureux à respecter),
• pas de pollution des motifs réalisés (ils sont protégés de cette dernière durant tout leur séjour sous la tête d'impression),
• pas de surépaisseur parasite sur l'arrière des motifs (tous les granulés passant entre les lèvres de la trémie et les zones non perforées de la bande sont récupérés par le dispositif d'aspiration),
• pas de limitation, autre que la taille des particules, des formes et des dimensions des motifs (possibilité de créer un écoulement de particules permanent, ne comportant aucun régime transitoire),
• possibilité de déposer des particules abrasives sans être limité par des phénomènes d'usure.

Compared to previous solutions, the invention therefore makes it possible to obtain, with a production speed comparable to that of techniques using the rotary frame, a large deposit (from 1000 to 3000 g / m2) of particles of large particle size (from a to three millimeters), and this by targeting products which have the following characteristics:

• very good longitudinal regularity of removal (no runout),
• very good transverse regularity of removal (no deformation of the lip / strip contact generator and no rigorous parallelism to be observed),
• no pollution of the patterns produced (they are protected from the latter during their entire stay under the print head),
• no parasitic excess thickness on the back of the patterns (all the granules passing between the lips of the hopper and the non-perforated areas of the strip are recovered by the suction device),
• no limitation, other than the particle size, of the shapes and of the dimensions of the patterns (possibility of creating a permanent flow of particles, comprising no transient regime),
• possibility of depositing abrasive particles without being limited by wear phenomena.

Claims (6)

1. Process for the production of complexes which can be used as floor coverings, which consists in successively depositing, on a coated substrate and in a defined pattern, granules of plastic, in compressing the complex thus produced and in heat-treating it so as to produce a homogeneous sheet which is then taken up, for example in the form of a long reel, and in which process:

   each colour of granules is distributed on the substrate in a defined pattern by means of an assembly comprising a sieve or screen consisting of a continuous belt (3), which is flexible and deformable and has a defined pattern for each colour of granule, kept under tension by means of guiding elements (1,4,6) placed to the rear of the said belt and positioned one with respect to another in such a way that it has a cross section in the form of a polygon, one of the sides of which is maintained parallel to and spaced away from the substrate (3) to be covered with granules, and is moved at the same speed and in the same direction as the said substrate;

   the granules are fed through the belt (3) by means of a vibrating hopper (2) comprising a chute having two rigid lips (12) in contact with the surface of the said belt (3) forming the sieve or screen, the tension in the belt (3) creating a compressive force distributed uniformly over the lips/belt contact generatrix;

   the excess granules (14a) passing between the lips of the hopper and the unperforated regions of the belt are recovered by suction.
2. Process according to Claim 1, characterized in that the deformable belt (3) has a similar structure to the screen-printing sheets used for a rotary frame, this belt being positioned on three holding rollers (1,4,6), two (4,6) of which define a plane parallel to and spaced away from the surface to be coated, and the third (1) of which, lying in the mid-plane of the two aforementioned rollers (4,6), tensions the said belt by a vertical displacement.
3. Process according to either of Claims 1 and 2, characterized in that the contact between the rigid lips (12) of the vibrating hopper (2) and the surface of the belt (3) forming a sieve or screen lies below the plane defined by the lower generatrices of the rollers.
4. Plant for the production of complexes which can be used as floor coverings, being in the form of an assembly comprising essentially means making it possible to deposit, on a coated substrate, granules of plastic which are then compressed and heat treated, so as to produce a homogeneous sheet which is then taken up in the form of a long reel, the said means making it possible to deposit the granules consisting of a succession of assemblies allowing various colours of granules to be distributed over the substrate in a defined pattern, each assembly comprising:

   a sieve or screen consisting of a continuous belt (3), which is flexible and deformable and has a defined pattern for each colour of granules, kept under tension by means of guiding elements (1,4,6) placed to the rear of the said belt and positioned one with the respect to another in such a way that it has a cross section in the form of a polygon, one of the sides of which is maintained parallel to and spaced away from the substrate (13) to be covered with granules, and is moved at the same speed and in the same direction as the said substrate;

   the granules are fed through the belt (3) by means of a vibrating hopper (2) comprising a chute having two rigid lips (12) in contact with the surface of the said belt (3) forming the sieve or screen, the tension in the belt creating a compressive force distributed uniformly over the lips/belt contact generatrix;

   a suction device (7) making it possible to recover the excess granules (14a) which pass between the lips of the hopper and the unperforated regions of the belt (3).
5. Plant according to Claim 4, characterized in that the deformable belt (3) has a similar structure to the screen-printing sheets used for a rotary frame, this belt being positioned on three holding rollers (1,4,6), two of which (4,6) define a plane parallel to and spaced away from the surface to be coated, and the third (1) of which, lying in the mid-plane of the two aforementioned rollers (4,6), tensions the said belt by a vertical displacement.
6. Plant according to Claim 5, characterized in that the contact between the rigid lips (12) of the chute and the surface of the belt (3) forming the sieve or screen lies below the plane defined by the lower generatrices of the rollers (4,6).

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